picodb(mssql): support all MSSQL pdo drivers

For MSSQL make all connection attributes optional.
Handle differing DB connection params based on driver used.
connection can be made via ODBC DSN or server/hostname
username/password can be embedded in DSN definition or simply
omitted and single-signon will be attempted.

libs/picodb/lib/PicoDb/Driver/Mssql.php

@@ -19,10 +19,6 @@ class Mssql extends Base
      * @var array
      */
     protected $requiredAttributes = array(
-        'hostname',
-        'username',
-        'password',
-        'database',
     );
 
     /**
@@ -53,13 +49,45 @@ class Mssql extends Base
      */
     public function createConnection(array $settings)
     {
-        $dsn = 'sqlsrv:Server=' . $settings['hostname'] . ';Database=' . $settings['database'];
+        $dsn = $settings['driver'] . ':';
 
-        if (! empty($settings['port'])) {
+        // exactly one of hostname/DSN needed, port is optional
-            $dsn .= ';port=' . $settings['port'];
+        if ($settings['driver'] == 'odbc') {
+            $dsn .= $settings['odbc-dsn'];
+        } else {
+            if ($settings['driver'] == 'dblib') {
+                $dsn .= 'host=' . $settings['hostname'];
+            } elseif ($settings['driver'] == 'sqlsrv') {
+                $dsn .= 'Server=' . $settings['hostname'];
+            }
+            if (! empty($settings['port'])) {
+                $dsn .= ',' . $settings['port'];
+            }
         }
 
-        $this->pdo = new PDO($dsn, $settings['username'], $settings['password']);
+        if (! empty($settings['database'])) {
+            if ($settings['driver'] == 'dblib') {
+                $dsn .= ';dbname=' . $settings['database'];
+            } elseif ($settings['driver'] == 'sqlsrv') {
+                $dsn .= ';Database=' . $settings['database'];
+            }
+        }
+
+
+        if (! empty($settings['appname'])) {
+            if ($settings['driver'] == 'dblib') {
+                $dsn .= ';appname=' . $settings['appname'];
+            } elseif ($settings['driver'] == 'sqlsrv') {
+                $dsn .= ';APP=' . $settings['appname'];
+            }
+        }
+
+        // create PDO object
+        if (! empty($settings['username'])) {
+            $this->pdo = new PDO($dsn, $settings['username'], $settings['password']);
+        } else {
+            $this->pdo = new PDO($dsn);
+        }
 
         if (isset($settings['schema_table'])) {
             $this->schemaTable = $settings['schema_table'];

libs/picodb/lib/PicoDb/DriverFactory.php

@@ -32,6 +32,10 @@ class DriverFactory
         switch ($settings['driver']) {
             case 'sqlite':
                 return new Sqlite($settings);
+            case 'odbc':
+                return new Mssql($settings);
+            case 'dblib':
+                return new Mssql($settings);
             case 'mssql':
                 return new Mssql($settings);
             case 'mysql':